Catalyst for synthetic-methanol production



:Patented Apr., 26, 1927.

UNITED STATES PAT ENT oFFIcE.

JOHN G. woonnurr AND eaovnn; nnoomrmnn, or measure, INDIANA, AB-

ORPORATION, or manna morn, INDIANA,

SIGNORS TO COMMERCIAL SOLVENTS C A CORPORATION OF MARYLAND.

CATALYST non symimrro-unrmonraonuorron.

Ho Drawing.

Our invention relates to the production of methanol by the high pressure catalytic combination'of oxides of carbon with hydrogen, and pertains more directly to the prepara- 6 tion and employment of improved catalysts in the process.

Methanol may be produced by combining oxides of carbon with hydrogen in the presence of a suitable catalyst at elevated tem- 10 perature and pressure. Carbon monoxide,

carbon dioxide, and mixture of the two oxides may be employed, these substances reacting-with hydrogen according to the following reactions Carbon monoxide-CO 2H ZCH OH, Carbon dioxide-410 3H 2OH,OH H 0 It is observed that when carbon dioxide is the oxide employed, one molecule of water is formed for every molecule of methanol produced. On the other hand when pure carbon monoxide is used, theoretically there is nothing produced by the reaction but methanol. Actually in pract ce pure carbon monoxide and pure carbon dioxide are both difi'icult to obtain economically, so that the methanol synthesis is car'ried out by reacting a mixture of carbon monoxide and carbon dioxide with hydrogen.

In addition to the reactions producing methanol there are, in the methanol synthesis, undesirable side-reactions which cut down the yield of the desired product. The principal side reaction which may occur is the formation of methane, which is illustrated below:

In addition to the methane side-reaction there are other side-reactions which sometimes occur in which there are produced esters, aldehyde's, organic acids, ketoncs, and hydrocarbons other than methane; these reactions occurring as the result of the polymerization or condensation of methanol or its decomposition products.

When a gas mixture comprising carbon oxides mixed with an excess of hydrogen produce methanol is passed over a catalytic substance comprising metals or their oxides at a pressure above atmospheresandat a temperature above 250 0, there is nearly Application filed June 21,

over the amount theoretically required to.

1928. Serial No. 117,812.

always produced some reaction between the gaseous components. The extent of this react on depends to some degree on space velocity, temperature, and pressure, but the lined, carbon oxides and some extent in all cases.

The substances formed by such a process depend, both as to identity and as to amount. almost ent rely on the nature and activity of the catalytic substance present. In general, hnely divided metals or mixtures of metallic oxides nonreducible to free metal under the conditionsof the methanol synthesis are catalytic substances which cause the production of more or less methanol. Iron and nickel and their oxides, while usefulv hydrogenating and dehydrogenating catalysts in many other instances, have in the past been deemed unsuitablefor employment as methanol catalysts on account of their strong methanatingaction which largely prevents methanol formation, the carbon oxides being reduced to methane.

We have discovered a new type of methanol catalyst which produces ahigher yield of methanol than those formerly emloyed in the art, and at the same time proh 'drogen react to uces a-very pure methanol, uncontaminated;

by by-products. An additional advantage accruing from the use of our catalysts is that the formation of methane in the processwith the consequent destruction of valuable hydrogen-is practically eliminated.

It is known that metaloxides, non-reducible or diflicultly reducible to metals under the conditions of the methanol reaction serve as satisfactory base or the formulation of met anol catalysts (U. S. Patent 1,558,559). For example the oxides of metals of the second group in the Po riodic Table of Elementssuch as zinc and magnesiummay be alternatively employed as principal catalysts, but since by themselves the oxides are not true catalysts they are combined with smaller quantities of catalyst promoterswhich in turn, may consist of other metallic oxides-of the Third to Seventh Periodic Table groups. For example, zinc oxideper seis not a suitable catalyst, but in admixture with a less basic metal oxide, such as the oxides of chromium, manganese, molybdenum, titanium, cerium, vanadium, tungsten, etc, the

fact remains that under the conditions out-- lprincipal materials in said additive oxides apparently acting as promoters, the mixture becomes a good catalyst for methanol production.

Similarly magnesium may be used to relace zinc in the production of such cataysts. In the prior .art the catalyst mixtures of this type uniformly contained a greater us. At least three theories may be used to account for the phenomenonnamely (1) The metallic halide acts as an ordinary promoter in increasing catalyst activto produce oxychloride compounds which, in turn, either serve as catalyst promoters, or may so modify the purely physical state of the mass as to produce a more active catalyst; I

(3) The metallic halide may bereduced by the high pressure contact with hydrogen and carbon oxides during the commencement of its use as a catalyst and the resultant finely divided metal may increase the catalyst activity, or alternatively, the metallic halide may first react with. some other metal producing the halide thereof, which ma be reduced in the same manner.

owever, the precise explanation for the improved result attained by the addition of metallic halides to methanol catalyst is not known and forms no part of our invention.

To produce our improved catalyst it is not necessary that the amount of metallic halide .added bear any exact weight relation to the remainin constituents of the catalyst, though t e amount of halide added should preferably be less than one chemical equivalent of the amount of principal metallic oxide present in the catalyst.

Our invention is of widespread usefulness in the methanol art and to further disclose it but in no manner to limit it beyond the limitations derived from the whole specification we append the following examples:

Our improved catalyst consist of the followin elements.

I. n oxide of a second group (Mendeleefis Periodic Table) metal;

II. An oxide of a'metalof the third to seventh group to serve as a promoter;

(2) The metallic halide interacts with other metallic oxides present in the catalyst- Magnesium oxide--vanadium oxidemagnesium fluoride.

Magnesium ox1de-chrom1um ox1dechromium chloride.

Strontium oxide-chromium oxide-zinc chloride.

Zinc oxidevanadium oxide-magnesium chloride.

In general, catalysts of this type are most efiective if the oxide of the second group metal is present in predominating quantity over the other, promotin oxide. However catalysts containing oxi es in the reverse ratio produce methanol and are included in our invention.

The addition of a solution of zinc chloride to a mixture of zinc oxide and chromium oxide, followed b a drying and re covery of the mass, pro uces a catalyst giving results superior to those known in the art. Similar improved catalysts are ob tained when other combinations ofsecond group metal oxides and metallic halides are combined-for example magnesium compounds.

As illustrative of our improved catalysts the following results are appended.

E wample I.

A catalyst base material is prepared by dissolving 8 kilograms of chromic nitrate (Cr(NO,),-9H,O) in 5 liters of water; add ing with stirring 5 kilograms of zinc oxide, evaporating the mass to dryness, and heating until'the chromic nitrate is converted to chromic oxide. The mixture is then broken up and sieved through a 65 mesh screen.

If a quantity of this material is mixed with 10% of dextrin or a similar agglutenating agent dissolved in 10 parts of water and the resultant mixture dried and broken up into granules, a catalyst is obtained such as is described in the prior art.

When a mixture of .carbon oxides and h drogen comprising, say 10% of carbon dioxide and of hydrogen at a pressure of 2200 pounds is passed'through 1000 cubic centimeters of such a catalyst at a space ve- 1 st will produce from 1.7-2.0 liters of con ensate per hour and this condensate will show about 55% of methanol, the remainder being substantially .pure water. Furthermore an analysis of the residual gases will show a diminution in methane formation.

Example II.

If the zinc halide mentioned in Example I is replaced by an equivalent quantity of magnesium chloride similar improved results will be obtained. The yield of conden- 1 sate may fall to about 1.6 liters per hour, the

methanol content being unchanged.

Example 11].

2200 grams of zinc oxide and 300 grams of chromic oxide are mixed in a solution of about 200 grams of zinc chloride and 250 grams of dextrin in 3 liters of water. The .mass is dried and broken up into granules. When a gas mixture comprising 10% carbon dioxide, 2% carbon monoxide, and

- 88% hydrogen is passed through 1000 cubic centimeters of the catalyst, at a temperature of about 3804-20 (l, at a space velocity of 75,000100,000 and at a pressure of 3000 pounds there will be produced, hourly, about 2 liters of condensate analyzing about 57% methanol.

In the absence of the zinc chloride the total volume of condensate will be reduced and the percentage yield of methonal will be greatly reduced.

E wample IV.

If in Example III, the zinc oxide is replaced by magnesium oxide, the resultant catalyst under similar operating conditions will produce about 1.5 liters of condensate per hour, the methanol content remaining about the same.

Ewample V. 2600 grams of zinc nitrate u c ent-uneters of this catalyst at a space position of our improved catalysts.

velocity of about 100,000, ,a temperature of about 400, and at a pressure of 2500-3000 pounds, there will be produced, hourly, about 1.5 liters of condensate analyzing about methanol.

I Ear/ample VI.

3900 grams zinc nitrate v Oa)2' 2 and 500 grams uranium nitrate 2( a)2' a' is dissolved in 5 liters of warm water. To this mixture is added sufficient postassium carbonate to precipitate all of the zinc and uranium as carbonate and basic carbonate.

The resultant precipitate is recovered, washed, dried, and moistened with a solution containing 200 grams zinc chloride. The mass is again dried, and is broken up into granules, whereupon it is ready for use.

When a gas mixture com rising 10% carbon dioxide and by rogen is passed at a space velocity of 75,000 over 1 liter .of catalyst granules at a pressure of 2500 pounds" and a temperature of 380440 C.

.there is obtained hourly about 3 liters of condensate analyzing about 48% methanol. A similar catalyst to which a metallic halide is not added gives a far smaller yield and conversion to methanol.

The s ecific examples we'have related are intended to display various phases of our invention and not to limit it. While in the above specific examples we have shown the use of metallic chlorides and metallic bromides, it should be understood that similar results are attained with other halides, though in general we prefer to employ chlorides on account of their relative nonvolatility and ready accessibility. There exists, of course, a possibility of almost infinite variety in changes of percentage com- We have observed however, that while changes in the proportionate amount of second group metal to promoter produce changes in catalyst eifectiveness, at the same time the presonce of a metal halide in the catalyst invariably produces greatly improved results.

It is, of course, 0 vious that one may replace a single second group oxide by a mixture of two such oxides. For example zinc oxide may be replaced by a mixture of zinc oxide a d magnesium oxide. Likewise instead of on mium oxide, ,one may employ a. mixture. Such changes are within the spirit of our invention and the appended claims.

An increased space velocity produces an increased hourly yield and an increase in operating pressure has the same effect. Likewise the use of pure carbon monoxide as distinguished from carbon dioxide or a mixpromoter oxide'such as chroall ture of the two results in an increased methanol percentage in the condensate, and,

since carbon monoxide seems to react more readily, an increased condensate volume.

Now having described our invent-ion, we claim the following as new and novel 1. A methanol catalyst comprising a plura'lity of ditficultly reducible second group metal oxides, a plurality of difiicultly reducible metal oxides from the third to seventh groups, and a metallic halide.

2. A methanol catalyst'comprising a difficultly' reducible second group metal bxide,

a difiicultly reducible oxide of the third to seventh groups, and a metallic halide.

3. A methanol catalyst initially compris in a diflicultly reducible second group metal ox1de, a diflicultly reducible oxide of the third to seventh groups, and a metallic halide.

4. A methanol catalyst initially comprising a difiicultly. reducible second group metal oxide, a lesser quantity of a difiicultly reducible oxide of the third to seventh groups, and a metallic halide.

5. A methanol catalyst initially comprising a diflicultly reducible second group metal oxide, a lesser quantity of a diflicultly reducible oxide of the third to seventh groups, and a. metallic chloride.

6. A methanol catalyst initially comprising a difiicultly reducible second group metal oxide, a lesser quantity of a diflicultly reducible metal oxide of the third to seventh groups, and a metallic halidein amount not exceeding one chemical equivalent of the second group oxide.

- mixture of hydrogen and carbon oxides at a' pressure in excess of 50 atmospheres and at an elevated temperature, over a catalyst initially comprising a mixture of diflicultly reducible oxides and a metallic halide.

11. A process for the production of synthetic methanol which comprises passing a pressure in excess of 50 atmospheres and at an elevated temperature, over a catal st initially comprising, a mixture of di cultly reducible oxides and a metallic chloride.

12. A process for the production of synthetic methanol which comprises passing a mixture of hydrogen and carbon oxides, at a pressure in excess of 50 atmospheres and at an elevated pressure, over a catal 1y comprising a mixture of zinc oxide, chromium oxide, and zinc chloride.

In testimony whereof we ailix our signatures.

JOHN C. WOODRUFF.

' initial-' GROVER BLOOMFIELD.

mixture of hydrogen and carbon oxides at a 

